Protector for electric circuits



Aug. 10, 1937. G. N. LEMMON PROTECTOR FOB ELECTRIC CIRCUITS Filed Oct.1, 1934 2 Sheets-Sheet 1 INVENTOR Filed Oct. 1, 1934 2 Shee ts-Sheet 2.ENVENTOR F ii. l l l I I mi i Waienteti Aug. 16, 193'? UNITED STATESEATENT GZFFW PROTECTOR FOR ELECTRIC CIRCUITS George N. Lcmmon, Homewood,Ala.

Application mm 1, 1934, Serial No. 746,384

9 Claims. (Cl. 200l26) The purpose of this invention is to preventsingle-phase operation of a three-phase circuit which is protected byfuses.

On such a three-phase circuit, when one line is opened by the blowing ofa fuse, the two other lines still carry single-phase current to suchmotors as are then in operation. This is undesirable, and my devicecauses the blowing of the fuses in both of the other lines in case anyone of the three lines becomes open-circuited by the blowing of a fuse.

This invention can be used when there is but one fuse for each'line butit is particularly useful when used in conjunction with repeater fuses,such as are shown in my Patent No. 1,954,634 issued April 10, 1934. Onsuch a repeater fuse. the No. 1' tube with its fuse-link is normally incircuit while the No; 2 and No. 3 tubes are in reserve position. Whenthe No. 1 fuse blows, its 20 tube drops open and then the No. 2 fusecloses up into circuit-closing position. Similarly, blowing the No. 2fuse brings No. 3 into circuit. If the No. 3 fuse also blows the circuitremains open until refused. A three-phase circuit pro- 25 tected byreepated fuses becomes single-phased only after the third fuse has blownin one of the three lines. Therefore my protector device is preferablyarranged so that it operates upon the blowing of the No. 3 fuse in anyone of the lines.

High voltage circuits cannot be opened successfully in free air; butwhen a fuse blows inside of an expulsion tube the explosive efiect stopsthe flow of current. When one of the No. 3 fuses has ruptured, myprotector device places a 35 short-circuit across all three lines of thecircuit.

This causes all the other fuses to blow and so leaves the circuit fullyopened instead of leaving it single-phased. The short-circuiting arms ofthe device are preferably connected solidly to- 40 gether and allgrounded; but if desired one or more resistance elements, properlyinsulated, can easily be included to limit the overload imposed when thedevice operates.

Referring to the drawings, Fig. 1 shows part 45 of a three-phase circuitwith three repeater fuses installed, together with my protector. Fig. 2is a side view of the same from the right side; Fig. 3

is a partial section, in larger scale, of the operating mechanism of theprotector; and Fig. i 50 is a similar front view of the mechanism, whileFig. 5 shows the grounding bar in operating position.

In Fig. 1 three incoming lines are indicated b i, 2 and 3, while linesto the load are indi- 55 cated at i, ii and ii. Dotted lines are usedavoid interference with parts of the protector itself. The three fusesnormally in service are l, 6 and 9. The fuse link 9' is in service, thefuse link i6" is in reserve position, and I6 shows a portion of theblown fuse link. Near the fuses is the grounding shaft Hi, to which areattached three ground-arms, H, H, II.

The trip-shaft I2 is near the ground-shaft, and both shafts aresupported by the housings ll, [3, l3. Near one end of the trip shaft isthe control-arm l4. Each housing also carries a tube I!) which has aprojecting plunger ll, so placed that the plunger will be struckwhenever one of the No. 3 fuse tubes, i6, I6, l6 blows its fuse-link anddrops to the open position l6. The ground-shaft I0 is partiallyrotatable and when so rotated moves all three ground-arms from theposition ii to H. Inside each housing If the shaft l2 has secured to itan arm I! and adjacent to this arm is twist-arm i9, supported on a studand biased towards I6 by the spring 21.

The arm I! has an end 22 which is held by the latch 23. A spring 24biases the latch 22 against release, and the extension 25 of the latcharm 23 is in line with the inside end ll of the plunger ll.

Inside the housing l3, the shaft i0 has secured to it an arm 26 which isbiased by the spring 21 to move the ground-arms H up to the position ll.Inside of one or more of the housings, the

arms l6 and 26 are connected by the link 28. A.

suitable stop 29 allows, the linkage ill-28 to come somewhat beyond thestraight-line. position. When in this position this linkage forms apositive toggle-lock to prevent rotation of 26 and iii. A latch 30pivoted on the pin 3| is biased by the spring 32 so that it can engagewith the stud 33 in the arm l8, thereby preventing backward rotation ofthe arm l8 and the shaft l2.

Supported by the end housing I! is the control arm I, which is movableto rotate the shaft 34 and the crank and pin 36 which are inside thehousing. This pin 36 engages against the arm I! so that it can rotate l8clockwise when I4 is moved from H to M as shown in Fig. 2, and when 36is thereby moved from the position shown in Fig. 3 by full lines to theposition shown by dotted lines. When the outside arm is in the positionN, the pin 36 is away from l8 and the end 36' is engaged with 30 so that30 is disengaged from the stud 33. In this position the device is readyto function.

Under such conditions l2 can be rotated, thereby releasing thetoggle-lock of the linkage arm It and the shaft II, in clockwise motion.

Operation is as follows: If one of the No. 3 tubes on any of therepeater fuses drops to the 5 position It its strikes I1 and drives l1against II. This releases 23 from 22, and fl rotates I9 against ll,moving the toggle-joint II and II beyond the center position. 'Ihereupon21 rotates II to the position 26, and this rotates l0 l0 and brings allthe ground arms to the position II, in connection with the conductors l,I, 6. Thereby the remaining fuses in the two other iinesare all blown,and the three-phase circuit is completely open. A contact member I maybe used to avoid any burning of the line conductor 8.

When the line trouble has been cleared the equipment is re-fused asfollows: With an insulated stick, the operator pulls down, It to It as afar as possible. This rotates It against II, and

10 so rotates the whole shaft l2 until every member II has been pushedback, tensing 2i and engaging 2! with 13. The stop 29 is reached by 28only after I! and 28 are ensu d. At the same time II has engaged with3!, locking the protector open. The man then re-fuses the repeaters inthe usual way placing the No. 1 tubes all in service and the No. 2 andNo. 3 tubes all in reserve position. He then pushes the control ,armfrom It up to ll, which lifts 30 away from 33 and ena gages it with thenotch, in so. The spring :2 acts to hold ll over 38'. thereby keepingthe arm ll up until it is forcibly pulled down.

The equipment is thus again set ready to operate automatically.

I am not limited to the methods of construction here shown. for thedetails can easily be modified in many ways without departing from thefundamental principle of my invention. Also my invention can beeasilyapplied to single fuses or to repeater fuseshaving other than three Iclaim:

i. A protector for electric circuits comprising a conductor, a pluralityof fuse containers connected to the conductor, a fuse within eachcontainer, an adjacent fuse in 'series with an adiacent conductor,together with automatic means to blow the adjacent fuse. the operationof said last means being initiated by motion of one of 50 the saidcontainers.

2. A protector for an electric circuit comprising automatic means toshort-circuit all the conductor-sot the circuit. a fuse in circuit witheach 2,089,887 II and II, whereupon the spring 22' rotates the of saidconductors, a container for each fuse, together with means operable bythe motion of one of the said containers to initiate the operation ofthe said automatic means.

3. A protector for an electric circuit comprising automatic means toshort-circuit all the conductors of the circuit, a plurality of fusesconnected to each of said conductors, a container for each fuse,together with means operable by motion of one of said containers toinitiate the action of said automatic short-circuiting means.

4. In combination, a conductor, a plurality of fuses connectedtherewith, another fuse adjacent thereto, automatic means operable uponthe rupture of a certain one of the first fuses to rupture the saidadjacent fuse.

5. Protection for electric circuits comprising a plurality of circuitconductors, a plurality of fuses associated with one of said conductors,a fuse associated with another of said conductors together withautomatic means to blow the last said fuse upon rupture of the last ofsaid plurality of fuses.

6. Protection for electric circuits comprising a plurality of circuitconductors, a plurality of fuses associated with each of saidconductors, together with automatic means operable upon the rupture ofall fuses associated with any one of the said conductors to rupture allof the fuses associated with one of the other said conductors.

7. Protection for electric circuits comprising a plurality of circuitconductors, a plurality of fuses connected to each of said conductors,together with automatic means operable upon the rupture of all fusesconnected to any one of the said conductors to rupture a fuse connectedto each of the other said conductors.

8. Protection for electric circuitscomprising a plurality of circuitconductors, a. plurality of fuses associated with each of saidconductors. together with automatic means operable upon the rupture ofall fuses associated with any one of the said conductors to rupture allof the other said fuses.

9. Protection for electric circuits comprising a plurality of adjacentconductors, circuit interrupting means in series with each conductor andoperable independently of each other, together with automatic meansoperable after a pre-determined number of operations of one of saidcircuit interrupting means to operate another of said circuitinterrupting means.

GEORGE N. LEMMON.

